Valve mechanism for unloading compressors



Marh n, 1941.

c. B. Erri-:s

'VALVE ECHANISll FOR UNLOADHG CONPRESSORS Filgdoct. 25,4939 2 3116918411991 1 lNvENToR Y .FITES Patented Mar. 11, 1941 UNITED STATES 'PATENT vALva MEcnANlsM-ron comanssons OFFICE A pxNG tion of Delaware Application October 25, 1939, Serial No. 301,102

4 Claims.

My invention relates to valve mechanism and' more particularly to a valve mechanism for unloading a compressor when the pressure in receiver connected therewith reaches a predetermined value.

One of the objects of my invention is to pro-- duce an improved valve mechanism which will automatically shut off the intake of a compressor when the pressure in the receiver reaches l0 a predetermined value an'd also vent the oil dome to atmosphere, which oil dome is associatedwith the compressor for lubricating-purposes and has the oil therein subject to the discharged compressed luid during the operation of the compressor.

Another and more specific object of my invention is to so construct the valve mechanismreferred to that the -venting of the 011 dome will be controlled by the suction created by the zo compressor when the intake of the compressor is automatically closed by the predetermined pressure built up in thereceiver.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which Figure 1 is a view, partly in section, of

a compressor provided with an oil dome and showing my improved valve mechanism associated therewith, and Figure 2 is an enlarged sectional view showing details of the valve mechanism.

Referring tothe drawings in detail, the rotary compressor is of. known construction .and comprises a stator i having eccentrically mounted therein -a rotor 2 secured to a drive shaft 3 journaled in the end plates 4 and B. The rotor 2 is provided'with a plurality of spaced slots 6 extending in an axial direction in which are mounted reciprocable blades 1 (one onlybeing o shown) biased outwardly into engagement with the inner surface of the stator by springs 8. The end plate 4 isprovided with an intake`passage 9 and the end plate! with an `outlet-passage I0. Secured to endplate 5 is an oil` reservoir -or 45 domev Ilwhich contains oil for the .purpose of lubricating the compressor.l In-the construction shown the shaft 3 of the compressor drives an oil pump I2 to pump oil from the body of oil through passage i3 and discharge it into a' well 50 il through the opening i5. Theoil in the well is free to ow through the passage I6 in shaft 3 and then into the compressor by wayvof the keyway i1 to thus provide lubrication vfor the (Cl. 23o-30) pressure during operation of the compressor, the body 'of oil in the oil dome is caused to be subject to the duid under pressure discharged from the compressor. This is accomplished by having. the discharge port I0 connected to a pipe |8 which extends above the oil line. Anv oil sep-- arator I9 removes any excess oil which may be discharged from the compressor together with the compressed air. The discharge port I0 has associated therewith a. checkvalve -20 for -prel0 venting any of the compressed air from returning to the compressor. The oil dome communicates with the compressed air-receiver or tank 2i by a conduit 22 and a check valve 2 3 prevents return oi compressed air to the dome. The la compressed airvmay be used for any purpose desired, as for example, the actuation of vehicle brakes.

In the type of compressor Just described the compressor is generally automatically unloaded 20 by shutting oi the intake when the receiver for the compressed air discharged by the compressor reaches a predetermined value and again allowed to compress air when the compressed air in the receiver falls to a given pressure below the pre.- 9,5 determined value. With such an arrangement it has been discovered that when the compressor is unloaded, an excess amount of oil' may be fed to the compressor .and cause it to become choked because of the compressed air acting 30 upon the oil and forcing it into the compressor.l It has also been discovered that the shutting oft' of the'compressor by closing the intake does vnot cause the compressor .to run idle since the compressor still operates to'compress the air re- 3 5 maining in the compressor which may be p artially discharged into the oil dome against the compressed air already therein or, if this lsnot accomplished due to insuiilcierit air to compress,

recirculated and recompressed continuously. 40- The result of the compressor being partially-un der load and performing work is that it will vcontinue to generate -heat and use power -notwithf standing no additional compressed airis. being added to the receiver. All of these undesirable 45 Y operating features present whenv the compressor rintake is shut cd1 can be eliminated to a large extent vbyjalso unloading the oil dome at the same time the intake is shut oil. With the air in the oil dome under atmospheric pressure, Viii) vthe oil forced into the t compressor' will be' .reduced and the air and oil being circulatedin the 4 compressor will be free to bedischarged into the oil dome against atmospheric pressure instead. oi' against compressed air. A'superior operating 56 mosphere lismounted on the compressor at the "intake passage 9 by bolts .25. The valve mechanismco'mprises a casing `28provided with a vertical bore 21 and a passage 28 for placing the intake passage in communication with the atmosphere through an air cleaner 29. The bore 21 adjacent the juncture oflpassage 28 has associated therewith a valve seat 38 for cooperation with a movable valve member 3| having an annular rib 32 for engagement with the valve seat.

The valve member is formed with a slotted skirt 33 which projects into the bore and is guided thereby. A spring 34 positioned in bore 21 normally biases the valve member to open position l against the threaded annular plug 35, this spring `abutting a' threaded adjusting member 38 whereby the tension of the springmay be adjusted as desired. 'Ihe upper end of the valve member extends through the plug 35 and carries a piston 31 which has associated therewith a diaphragm 38. This diaphragm is sealed against the top of plug 35 by an annular ring 39 and spring 40 interposed between the ring and a closure plug 4|l forming with the casing a chamber 42 above the diaphragm. This chamber communicates with a passage 43 in the casing and the passage is connected by a conduit 44 with the compressed dome and passage 28 which, as previously stated,

is in communication with the atmosphere through the air cleaner 29. The valve element 48 is mounted by a guide sleeve 58 on the casing and the outer end of the valve member has connected thereto a diaphragm 5| which is sealed to the casing by a cap 52, the latter forming with the diaphragm, a chamber 53; The conical end4 49 of the valve member is normally heid engaged with the end of passage 41 by means of a spring 54 interposed between the diaphragm and the cap 52. A passage 55 in the casing places the chamber 53 in constant communication with the .bore 21 at a point between the valve member 3| and the intake passage 9 leading to the compres- When the compressor is operating, the parts of the valve mechanism are in the positions shown in Figure 2. Under these conditions air is free to pass through 'the air cleaner 29, passage 28,

past the open valve member 3 I and into the compressor where it is compressed andl discharged into the top o! the oil dome. Since the valve element 48 is biased to closed position, the oil dome will be sealed and the compressed air in f the dome will pass into the air tank. In the valve mechanism shown, the spring 34 is adjusted so that the valve member 8I-Will remain open 'I5 until a predetermined pressure of one hundred pounds per square inch is eective in. chamber 42 and also in the tank since thisl chamber is in constant communication with said tank. The spring 54 is of such strength that the valve member 48 will be held in closed position against the pressure in the oil dome. l

With the compressor operating the pressure in the air tank and chamber 42 of the valve mechanism will ultimately be raised to one hundred pounds per square inch. When this occurs, 'the piston 81 will be forced downwardly, thereby lmoving the valve member 3l -to closed position against seat 30. As the intake passage of the compressor is being cut oir,- a partial vacuum will begin'to exist in the intake passage and the bore 21 which'will cause the valve member to be pulled onto its 'seat at a rapid rate.

uum in bore 21 becomes quite high and since chamber 53 is in communication -with lthe bore,

the same partial vacuum will be present therein.

This will`cause the atmospheric pressure in passage 28 to move the diaphragm against the spring 54 and cause the valve element 48 to open passage 41 and place the dome in communication with the atmosphere through. the air cleaner. With the air in the dome at atmospheric pressure the oil in well I4 will no longer be forced into the compressorunder a pressure. Any air remaining in the compressor; after the valve member 3| has become closed will be compressed and easily forced-out into the oil dome through the outlet port check valve 28 which is no longer subject to a closing torce by iluid under pressure. The compressor will now run idle since it is substantially completely unloaded. The power necessary to run the compressor will be a minimum and due to the fact that there will be no load imposed upon the blades, the temperature of the compressor and oil will drop substantially. Also, since the compressor is not doing. any work under these conditions, it is not necessary to `have a great amount of oil in the compressor.

The oil that iiows by force of gravity into the compressor is suilicientfor lubrication and not so excessive as to choke up the compressor.

When the compressed air in tank 2| is used and the pressure therein drops to such a value that the spring 34 can move the valve member 3| sofi its seat against the action of the vacuum nin the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having i'ully described my invention, what I claim'as new. and desire to secure by Letters Patent or theh United States is:

1. In combination with a compressor provided with an intake port and a discharge port and having associated therewithv an voil reservoir communicating with the compressor lfor providing lubricant ior the. working parts ot the When the valve l member 3| is completely closed, the partial vaccasein compressor and wherein' the oil in the reservoir is subject to the discharged compressed iluid from the compressor prior to passage to a receiver, automatically operable means comprising a valve for closing the intake port when the fluidv pressure in the receiver is a predetermined value, and

means controlled by the suction created by the compressor when the intake port is closed for causing the oil reservoir to'be ventedto atmosphere.

2. In compressed air storage apparatus comprising a receiver and anair compressor provided with intake and discharge ports, an intake shut-oli valve operative under condition of predetermined pressure in the receiver to close the intake port, a valve for placing the discharge port in communication with theatmosphere, and

means for operating said last named valve, said Y means being made eiective by suction produced by continued operation of the compressor after the intake port is closed. i f

3. In compressed air storage apparatus comprising a receiver and-a rotaryaircompressor "a provided with intake and discharge ports. anin' take shut-oi! valve operative under condition of predetermined pressure inthe receiver to close .the intake port, a valve for placing the discharge with intake and discharge ports, an intake shut-A oii valve operative under conditions of predetermined pressure in the receiver to close the intake port, a valve'for placing the' discharge port in communication with the atmosphere, said valve being resiliently biased to closed position, and means for opening vsaid valve, said means being operated by subatmospheric pressure created by 20 the compressor after theintake valve is closed.

` CYRIL B. Frrns. 

